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University of Iowa News Release

Aug. 12, 2004

UI Professor Tracks Origins Of Dinosaur Size

How did the dinosaurs become so big?

That's a question that Christopher Brochu, assistant professor of geoscience in the University of Iowa College of Liberal Arts and Sciences, and his colleagues attempt to answer in an article published in the Aug. 12 issue of the journal Nature.

In the article, Brochu and his colleagues write, "T. Rex's great stature was primarily attained by accelerating growth rates beyond that of its closest relatives."

By studying the growth rings in non-weight-bearing fossilized bones -- including ribs -- of Tyrannosaurus rex, they learned that the best-known species of the large carnivorous dinosaurs grew very rapidly during its teenage years, gaining about five pounds per day over a period of about four years. That's roughly 7,000 pounds and more than half of its adult weight.

The authors note that the adult Tyrannosaurus rex, weighing 11,000 pounds and more, was one of the largest carnivorous creatures, growing to maturity in about 20 years and living some 28 years. Perhaps the best example of a T. rex is "Sue," the largest and most complete T. rex skeleton yet uncovered and a specimen Brochu worked on at The Field Museum in Chicago. Coincidentally, Brochu notes that the Nature article was published on the 14th anniversary of Sue's Aug. 12, 1990 discovery.

Why study dinosaurs at all? Brochu says that the public is fascinated with dinosaurs, and that is why he has taught a class on dinosaurs for undergraduate non-majors at the UI. He adds that T. rex is something of an ambassador for science by giving researchers an opportunity to do science that is of interest to the public.

Brochu, who came to the UI in 2001, earned his bachelor's degree in geology from the UI in 1989 and his master's and doctorate from the University of Texas at Austin in 1992 and 1997, respectively. From 1998 through 2000, he was a postdoctoral research scientist at The Field Museum, where his primary duty was the completion of a monographic description of Sue.

At the UI, his research focuses on the evolutionary history of fossil and living archosaurs, especially crocodiles and theropod dinosaurs, and the comparison of molecular and fossil-based methods of estimating divergence times between evolutionary lineages. He also teaches courses in vertebrate paleontology.

Brochu's co-authors are: Nature article lead author Gregory M. Erickson, Department of Biological Science, Florida State University, and the Division of Paleontology, American Museum of Natural History, New York; Peter J. Makovicky, The Field Museum, Chicago; Philip J. Currie, Royal Tyrrell Museum of Paleontology, Drumheller, Alberta, Canada; Mark A. Norell, Division of Paleontology, American Museum of Natural History, New York; and Scott A. Yerby, Division of Biomechanical Engineering, Stanford University, Stanford, Calif. The National Science Foundation and the Florida State University College of Arts and Sciences funded their research.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500.

CONTACTS: Gary Galluzzo, 319-384-0009,